Thanks for your suggestions, potpourri.
Maybe I need to give more background.
(1) Although dd is verbal, she doesn’t tell her brother to do anything except “be quiet” or “stop,” so I don’t know how well making him her slave for a day would work.
(2) We have just begun training ds in doing chores. So far he dusts and cleans mirrors/computer screens and is supposed to pick up clutter and that’s about it. Dd doesn’t do chores yet except help pick up clutter.
As to her “quirks,” I can’t put my finger on anything else at the moment. We’re having some food issues that we haven’t had before, but I’m not sure if this is sensory or just stubbornness.